Brakes slowly lock up after driving 10 miles

[roscoscott]

75 Z

I installed a new brake booster, 4 piston calipers on the front, disk on the back and a master cylinder off a 82 Z.

problem:

After putting on brakes in stop and go traffic for about 10 miles the brakes get stiffer and stiffer until they lock up. I can unbolt the master cylinder and the wheels will turn again. bolt it back on and drive again and does it again.

question:

What is going on man!

Is the booster defective?

Please help

[LeonV]

There is a check valve in you master for the rear circuit. It was needed for the drums but not so for the disks. Take it out and you should be good to go.

[cbuczesk]

You might need to adjust the pushrod coming out of the booster that projects into the master cylinder. Make it shorter by 5mm and try driving it. I had the same problem.

Chuck

[olzed]

I had this same problem, and the front brakes were locking. If I released the master front bleeder it was OK for a while. The problem was the master cylinder.

Perhaps you could try your original master cylinder to isolate the problem.

[roscoscott]

I tried to adjust the rod but it did the same thing...

[roscoscott]

I'll try this today. Thanks

[roscoscott]

There is a check valve in you master for the rear circuit. It was needed for the drums but not so for the disks. Take it out and you should be good to go.

The check valve is in the master?

[zKars]

Still have the push rod length too long me thinks.

Might want to check out this thread on Hybridz.

http://forums.hybridz.org/index.php/topic/102754-a-one-inch-diameter-brake-master-cylinder-for-the-s30-z-cars/

It has a section on properly setting the length of the push rod.

At the bottom of post #1 is a link that contains an excellent article on the subject. Definitely worth reading.

Other than that its the master itself that may be bad.

Edited August 31, 2012 by zKars

[Diseazd]

I agree with Cbuczesk and Zcars........your pushrod is too long. You need to readjust to a shorter length.......your master cylinder is holding your pads against your rotors at all times. This in turn heats the rotors and expands the calipers causing your brakes to finally lock up. Be careful....it can get so hot that it warps your rotors. IMO

[roscoscott]

The push rod wouldn't adjust. (It's stuck) So I put two washers in-between the master and booster. I drove it around the 10 mile loop and they progressively got tighter and tighter until they finally locked up. I unbolted the master and the wheels freed up.

[cbuczesk]

Try 4 washers. Mine locked up at work and all I had were some pennies to use as spacers. Best of all I got to do it in the dark!

Chuck

[roscoscott]

Try 4 washers. Mine locked up at work and all I had were some pennies to use as spacers. Best of all I got to do it in the dark!

Chuck

It happened to me at a red light. I read a few post in the Hybrid and they say the same thing. I'll try it this weekend.

Thanks for the help